Bottom Line:
Gypsum was the only phase found in the composition of both pure and gypsum:Sr, meanwhile a shift into lower diffraction angles was observed in the X-ray diffraction patterns of doped specimens.Compared to pure gypsum, the osteoblasts cultured on strontium-doped samples showed better proliferation rate and higher alkaline phosphatase activity, depending on Sr concentration.These observations can predict better in vivo behavior of strontium-doped gypsum compared to pure one.

ABSTRACTThis paper describes some physical, structural, and biological properties of gypsum bioceramics doped with various amounts of strontium ions (0.19-2.23 wt%) and compares these properties with those of a pure gypsum as control. Strontium-doped gypsum (gypsum:Sr) was obtained by mixing calcium sulfate hemihydrate powder and solutions of strontium nitrate followed by washing the specimens with distilled water to remove residual salts. Gypsum was the only phase found in the composition of both pure and gypsum:Sr, meanwhile a shift into lower diffraction angles was observed in the X-ray diffraction patterns of doped specimens. Microstructure of all gypsum specimens consisted of many rod-like small crystals entangled to each other with more elongation and higher thickness in the case of gypsum:Sr. The Sr-doped sample exhibited higher compressive strength and lower solubility than pure gypsum. A continuous release of strontium ions was observed from the gypsum:Sr during soaking it in simulated body fluid for 14 days. Compared to pure gypsum, the osteoblasts cultured on strontium-doped samples showed better proliferation rate and higher alkaline phosphatase activity, depending on Sr concentration. These observations can predict better in vivo behavior of strontium-doped gypsum compared to pure one.

fig9: Cumulative concentration of Ca (a) and Sr (b) ions released from various Sr-doped specimens into the SBF solution.

Mentions:
The ion release of gypsum ceramics in the SBF solution is shown in Figure 9. This experiment was carried out with periodic exchange of SBF solution and the results are presented as cumulative concentration of Ca (Figure 9(a)) and Sr (Figure 9(b)) against the immersion time. According to Figure 9(a), the concentration of Ca ions released from all gypsum specimens is much higher than that of other calcium phosphates reported in other studies [26]. It originates from the higher solubility and thus higher bioresorption rate of calcium sulfate-based materials in comparison with other well-known bioceramics such as β-tricalcium phosphate and hydroxyapatite. The concentration of Ca2+ ions released from pure gypsum (G-0) into the SBF solution was slightly higher than that of gypsum:Sr specimens. Since the calcium concentration is proportional to resorption rate of such bioceramics, the results demonstrate that incorporation of strontium ions into gypsum can diminish the biomaterial resorption rate. This decreased degradation rate of gypsum:Sr indicates higher chemical stability of these materials compared to pure gypsum. It is suggested that this is due to the complicated movement Ca ions in the crystal when encountering with Sr ions having larger atomic radius. The higher bonding strength of Sr-sulfate group in comparison with Ca-sulfate group should not be ignored too (note that Sr is more electronegative than Ca [27]). Calcium sulfate-based bioceramics have been used as potential materials for bone tissue regeneration, because of their adequate biocompatibility and osteoconductivity. However, the high degradation rate of these materials is the main practical problem [28], resulting in material to be lost in defect site before the completion of tissue repair. Incorporation of strontium into gypsum may control its too fast resorption rate to some extent.

fig9: Cumulative concentration of Ca (a) and Sr (b) ions released from various Sr-doped specimens into the SBF solution.

Mentions:
The ion release of gypsum ceramics in the SBF solution is shown in Figure 9. This experiment was carried out with periodic exchange of SBF solution and the results are presented as cumulative concentration of Ca (Figure 9(a)) and Sr (Figure 9(b)) against the immersion time. According to Figure 9(a), the concentration of Ca ions released from all gypsum specimens is much higher than that of other calcium phosphates reported in other studies [26]. It originates from the higher solubility and thus higher bioresorption rate of calcium sulfate-based materials in comparison with other well-known bioceramics such as β-tricalcium phosphate and hydroxyapatite. The concentration of Ca2+ ions released from pure gypsum (G-0) into the SBF solution was slightly higher than that of gypsum:Sr specimens. Since the calcium concentration is proportional to resorption rate of such bioceramics, the results demonstrate that incorporation of strontium ions into gypsum can diminish the biomaterial resorption rate. This decreased degradation rate of gypsum:Sr indicates higher chemical stability of these materials compared to pure gypsum. It is suggested that this is due to the complicated movement Ca ions in the crystal when encountering with Sr ions having larger atomic radius. The higher bonding strength of Sr-sulfate group in comparison with Ca-sulfate group should not be ignored too (note that Sr is more electronegative than Ca [27]). Calcium sulfate-based bioceramics have been used as potential materials for bone tissue regeneration, because of their adequate biocompatibility and osteoconductivity. However, the high degradation rate of these materials is the main practical problem [28], resulting in material to be lost in defect site before the completion of tissue repair. Incorporation of strontium into gypsum may control its too fast resorption rate to some extent.

Bottom Line:
Gypsum was the only phase found in the composition of both pure and gypsum:Sr, meanwhile a shift into lower diffraction angles was observed in the X-ray diffraction patterns of doped specimens.Compared to pure gypsum, the osteoblasts cultured on strontium-doped samples showed better proliferation rate and higher alkaline phosphatase activity, depending on Sr concentration.These observations can predict better in vivo behavior of strontium-doped gypsum compared to pure one.

ABSTRACTThis paper describes some physical, structural, and biological properties of gypsum bioceramics doped with various amounts of strontium ions (0.19-2.23 wt%) and compares these properties with those of a pure gypsum as control. Strontium-doped gypsum (gypsum:Sr) was obtained by mixing calcium sulfate hemihydrate powder and solutions of strontium nitrate followed by washing the specimens with distilled water to remove residual salts. Gypsum was the only phase found in the composition of both pure and gypsum:Sr, meanwhile a shift into lower diffraction angles was observed in the X-ray diffraction patterns of doped specimens. Microstructure of all gypsum specimens consisted of many rod-like small crystals entangled to each other with more elongation and higher thickness in the case of gypsum:Sr. The Sr-doped sample exhibited higher compressive strength and lower solubility than pure gypsum. A continuous release of strontium ions was observed from the gypsum:Sr during soaking it in simulated body fluid for 14 days. Compared to pure gypsum, the osteoblasts cultured on strontium-doped samples showed better proliferation rate and higher alkaline phosphatase activity, depending on Sr concentration. These observations can predict better in vivo behavior of strontium-doped gypsum compared to pure one.